System of controlling electron current in multiple electrode tubes



1956 KOlCHl MIYAJI SYSTEM OF CONTROLLING ELECTRON CURRENT IN MULTIPLE ELECTRODE TUBES Filed Sept. 5, 1950 I N VENTOR ATTORNEYS United States Patent SYSTEM OF CONTROLLING ELECTRON CURRENT IN MULTIPLE ELECTRODE TUBES Koichi Miyaji, Tokyo, Japan, assignor to Japan Broadcasting Corporation, Tokyo, Japan Application September 5, 1950,'Serial No. 183,131 Claims priority, application Japan October 7, 1949 4 Claims. (Cl. 250-36) This invention relates to improvements in a system of controlling electron currents in multi-electrode tubes, particularly apentode, and has for its principal object to provide anamplifying'and-oscillating system adapted for use with'ultra-high frequencies or for a wide band transmission.

Another object of this invention is to provide a multielectrode valve, particularlya 'p'entode, adapted to be used for ultra-high frequency circuits without extremely reducing the distance between electrodes as in heretofore known vacuum valves of this kind.

Further object of this invention is to provide a variable impedance device adapted for use with ultra-high frequencies by utilizing a virtual cathode.

Yet a more specific object is to provide with a pentode for ultra-high frequency applications having a cathode, a first, a second and a third grid, and an anode spaced in that order from the cathode, the anode and the second and third grids being disc-sealed; a first cavity resonator connected between the second and third grids, and a second cavity resonator connected between the third grid and anode, there being direct current potential means maintaining the anode and second grid at positive potentials with respect to the cathode and third grid in order to establish a virtual cathode between the second and third grids and in order to make the conductance between the second and third grids substantially Zero at the operating frequency.

It is a well known fact that the space charge controlling system is used in a majority of electron current controls. In the diode, triode, and other multi-electrode tubes, the control of electron current is made under space charge limitation, the tubes performing operations of detectors, oscillators, amplifiers, mixers, modulators, etc. When the employed frequency is increased, or when the object is a Wide band, however, operations of vacuum tubes are obstructed and become inefficient through various causes as is well known. These causes can be roughly divided into two main causes: Namely, in the circuit and in the characteristics of electrons. The first trouble is almost entirely eleminated at present with the combination of suitable distribution circuits with miniature tubes, disk-seal tubes, etc. The latter fault is a fundamental problem of the internal construction of vacuum tubes, and the higher the employed frequencies as a result of progress made in the art of disk-seals and other contrivances, the greater the problem. In other words, because of the time spent in the transit of electrons travelling from one electrode to another, the tube characteristics are impaired considerably. The only known method at present to alleviate such influence is to reduce inter-electrode distances, shorten electron transit time and enlarge tube conductance. in the diode system, the distance between the anode and cathode is to be reduced, and in the triode and multi-grid tubes, it is to reduce especially the distance between the cathode and the first grid. This, however, necessitates a higher proficiency in the manufacture of tubes and in the use of materials of superior quality, or in other words, precise manufacturing technique and special materials. Even if such difiiculties were'overcome in the manufacture, other stumbling blocks will arise, such as short-circuiting during'use of the apparatus, non-unifo'rmity of manufactured articles, etc., and enlargement of the inter-electrode capacity cannot be prevented. As a result of recent progress of disk-seal tubes, even in ultra-high frequency systems, the former space-charge control system, in comparison with other electron current control systems, is being reconsidered, but apparently insurmountable difiiculties have been encountered in 'attempting'to adapt the process of the former days to the new tubes.

For a better understanding of my invention, reference is taken to the accompanying drawings which illustrate several embodiments of my invention. In the drawing,

Fig. 1 is a diagrammatic view of the pentode valve embodying the invention;

Fig. 2 is a'sectional elevation of an amplifier with a disk-sealed pentode and a cavity resonator; and

Fig. 3 is also a sectional elevation of an oscillator embodying this invention as a modified form of Fig. 2.

With reference now to Fig. 1, the amplifier circuit includes a pentode V2 seen to be comprised of a cathode 16, a'first-grid 17, a second grid 18, a third grid 19 and an anode 20. Condensers C for blocking direct current are included in the several grid circuits. An input cavity resonator Z1, having input terminals 14, 15 is connected between the second and third grids, 18, 19 and an output cavity resonator Z2, having output terminals 21, 22 is connected between the third grid 19 and the anode 20. Direct current potential means, shown as batteries 30-33 are provided to maintain the anode 2.0 and second grid 18 at positive potentials with respect to the cathode 16 and third grid 19 in order to establish a virtual cathode between the second and third grids and to make the potential between the second and third grids i. e. the input conductance between the second and third grids substantially zero at the operating input frequency. The input and output cavity resonators Z1, Z2, respectively are substantially resonant at the operating frequency.

Fig. 2 shows more of the structural detail of the tube V2 and the input and output cavity resonators Z1 and Z2, the various elements having the same reference numerals as those shown in the schematic view of Fig. 1. The anode 20 and the second and third grids 18, 19 are disc-sealed as a whole with respect to the first grid 17 and cathode 16 by means of two metallic discs sealed to the enevelope at a position adjacent the anode and at another position between the first and second grids. The input loop to resonator Z1 is shown at 23 and the output loop from resonator Z2 is shown at 23'. The terminals for the second and third grids and for the anode are indicated at 24, 25 and 26 respectively.

The amplifier of Fig. 2 may be modified as shown in Fig. 3 to operate as an oscillator. The modifications required comprise omission of the input loop 23 of Fig. 2 and the addition of a back coupling loop 28 between the inner and outer cavity resonators Z1 and Z2.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

l. The combination with a pentode of the disc-sealed type for ultra high frequency purpose having an envelope, a cathode, a first, a second and a third grid and an anode spaced in that order from the cathode, of a first cavity resonator connected between the second and third grids, and a second cavity resonator connected between the third grid and anode said first and second cavity resonators being substantially resonant at the operating frequency, and direct current potential means maintaining said anode and second grid at positive potentials with respect to said cathode and third grid to establish a virtual cathode between said second and third grids, and to make the conductance between said second and third grids substantially zero at the operating frequency.

2. A pentode of the disc-sealed type for ultra high frequency amplifier use having a cathode, a first, second and a third grid and an anode spaced in that order from the cathode, in combination with an input cavity resonator connected between the second and third grids, and an output cavity resonator connected between the third grid and said anode said input and output cavity resonators being substantially resonant at the frequency of the input signal, and direct current potential means maintaining said anode and second grid at positive potentials with respect to said cathode and third grid to establish a virtual cathode between said second and third grids, and to make the conductance between said second and third grids substantially zero at the operating frequency.

3. A pentode of the disc-sealed type for ultra high frequency oscillator use having a cathode, a first, a second and a third grid and an anode spaced in that order from the cathode, in combination with a first cavity resonator connected between the second and third grids, and a second cavity resonator with output circuit connected between the third grid and anode said first and second cavity resonators being substantially resonant at the frequency of the output signal, a feed back coupling provided between said first and second cavity resonators, and direct current potential means maintaining said anode and second grid at positive potentials with respect to said cathode and third grid to establish a virtual cathode between said second and third grids, and to make the conductance between said second and third grids substantially zero at the operating frequency.

4. The invention as recited in claim 1, wherein said second cavity resonator surrounds and encloses said first cavity resonator.

References Cited in the file of this patent UNITED STATES PATENTS 1,958,027 Wheeler May 8, 1934 1,975,143 Farnesworth Oct. 2, 1934 2,015,327 Wheeler Sept. 24, 1935 2,141,673 Thompson Dec. 27, 1938 2,239,677 Jobst Apr. 29, 1941 2,294,782 Jacobsen Sept. 1, 1942 2,342,986 Bosch Feb. 29, 1944 2,441,254 Stromeyer May 11, 1948 2,452,337 Strutt Oct. 26, 1948 2,506,265 Brian May 2, 1950 2,579,820 Haller et a1 Dec. 28, 1951 FOREIGN PATENTS 625,273 Germany Feb. 6, 1936 464,977 Great Britain Apr. 26, 1937 OTHER REFERENCES Ser. No. 374,712, Strutt (A. P. C.), published May 25, 1943. 

